1. Field of Invention
The present invention relates generally to the field of wireless communication and data networks. More particularly, in one exemplary aspect, the present invention is directed to compensating for and/or mitigating the effects of electro-magnetic signal interference in devices implementing multiple wireless air interfaces or protocols.
2. Description of Related Technology
The effective implementation of convergence products has led to a revolution in the way consumers view computerized devices. These next generation computerized devices focus on offering consumers a substantially unified solution for a variety of services to which consumers have become accustomed. Examples of such a converged solution include the exemplary MacBook Air™ laptop computer, MacBookPro™, and iMac™ desktop, and iPhone™ smartphone, each manufactured by the Assignee hereof, and each of which support a variety of wireless protocols and other functions. For instance, the aforementioned iPhone smartphone has the capability of, among other things, sending and receiving data over a Wireless Local Area Network (WLAN) such as a Wi-Fi network, making and receiving calls using a cellular network such as a Global System for Mobile Communications (GSM) network, and operating wireless peripheral equipment (such as wireless headsets or Human Interface Devices (HIDs)) using a Personal Area Network (PAN) such as a Bluetooth network. Similarly, the aforementioned Macbook Air provides high speed WLAN capabilities in conjunction with wireless PAN accessory functionality (mouse, keyboard, etc.)
As product form factors shrink, implementation requirements and constraints (including cost, size, and antenna isolation) in these hardware systems inevitably introduce difficulties which can potentially result in a poor user experience with the device. For example, both Bluetooth and Wi-Fi (802.11b/g/n) can operate within the 2.4-2.4835 GHz frequency range, and when used simultaneously in close proximity, will often interfere with each other. This interference can cause operational problems which may be perceptible to the user, such as Bluetooth audio stutter and drop-outs, slow Wi-Fi transfer speeds, poor Bluetooth mouse (MS) or trackpad tracking, MS or trackpad or keyboard link dropouts, etc., thereby degrading user experience (and potentially affecting other aspects of operation).
New technologies will continue to exacerbate such coexistence problems by further crowding the available radio spectrum. For instance, incipient changes to Wi-Fi standards offer higher order Multiple Input Multiple Output (MIMO) type antenna operation. Future implementations of Wi-Fi will support both 2×2 operation (two (2) receive antennas, two (2) transmit antennas) and 3×3 operation (three (3) receive antennas, three (3) transmit antennas). Changes to the Bluetooth protocol will increase transmit power (e.g., 10-20 dBm). Yet other emerging technologies, such as Zigbee™, Wireless Universal Serial Bus (USB), WiMAX, etc. will further crowd the same radio spectrum.
Existing solutions have relied on “time division coexistence” to manage RF interference between different protocols. Time division coexistence allocates each radio exclusive access to the radio resource over a specific time interval. However, time division coexistence has certain limitations. Consider for example, a 3×3 Wi-Fi modem that can achieve over 200 Mbps, in conjunction with a Bluetooth modem that operates at 3 Mbps. Most Bluetooth applications are used in wireless user interface accessories (e.g., mono and stereo audio applications, etc.), and are prioritized over the data-intensive Wi-Fi packets. Since Wi-Fi cannot operate during the higher priority Bluetooth time intervals, the 3×3 Wi-Fi modem can only support data rates far below its actual capabilities.
Therefore, improved methods and apparatus for device coexistence are needed. In particular, improved solutions should maximize performance for simultaneous operation of multiple radio technologies operated in close proximity, without suffering from the disabilities associated with time division coexistence.